Exhaust steam injector



R. D. METCALFE Ei-Ai, 2,261,854

EXHAUST STEAM INJECTOR I 7 Filed July 23, 1940 2Sheets-Sh6et 1 Nov. 4, 1941. R. D. METCALFE ETAL 2,261,854 EXHAUST S-TEAM INJECTOR Filed July 25 1940 2 Sheets-Sheet 2 a wev ca/ Patented Nov. 4, 1941 UNITED STATES PATENT OFFICE EXHAUST STEAM INJECTOR Richard David Metcalfe and James Croxon Metcalfe, Romiley, England, assignors to Davies & Metcalfe Limited, Romiley, England, a British company 2 Claims.

This invention relates to exhaust steam injectors and is concerned with the supply of boiler or live steam which is throttled down to low pressure and serves to work the injector when exhaust steam is not available. Usually a nozzle or choke tube is provided between the branch containing boiler or live steam and the valve, called the automatic shuttle valve, which controls the fiow of the throttled down live steam to take the place of exhaust steam when the engine which supplies the latter is not functionmg.

In accordance with our present invention, we provide an automatic auxiliary choke which regulates the area for the flow of live steam to take the place of exhaust steam in accordance with the pressure of the live steam.

Referring to the accompanying explanatory drawings:

Figure l is a longitudinal section and. Figure 2 a cross section on the line 2--2 of Figure 1 showing an exhaust steam injector having our invention applied thereto in one convenient form.

a indicates the inlet for exhaust steam, b, b the double beat valve for controlling the inflow of the exhaust steam, c the supplementary live steam inlet nozzle, d the inlet for live steam throttled down to low pressure which is used to work the injector when exhaust steam is not available, and e the adjustable cone for controlling the infiow of water to the injector, the adjustment of such cone being effected by the spindle f having a crank pin g on its end which enters a hole in a bush h let into the cone e. The

spindle 1 also turns the water out off valve 2'.

There are two further fixed cones 9' and k in advance of the combining nozzle m which has a hinged flap n therein. is the delivery nozzle.

The live steam inlet branch to the injector is at 1) (Figure 2). Such steam can pass directly to the nozzle 0 and can pass by way of the choke tube t to the passage 7 and thence, under the control of the automatic valve s, to the space at before referred to.

The quantity of steam (known as the auxil iary steam) admitted to the chamber d is determined by the bore of the choke tube t and the boiler pressure.

To keep the auxiliary steam pressure approximately constant with fluctuating boiler pressure, the efiective choke tube area should vary inversely with the boiler pressure.

The choke tube 15 and its internal spindle q constitute what we term an automatic auxiliary choke which gives an automatic adjustment of the steam flow area from the branch p, to the passage 7 and space it varying with the pressure in branch p so that such area is reduced with increase in the pressure of the live steam pressure in p and vice versa. The spindle q with a conical or stepped end portion is fitted concentrically within the choke tube t. The enlarged end of the spindle q (which is within a chamber at in communication with chamber r) is guided by a stem v and is flanged to receive the end of a compression coil spring w.

There is a balancing action between the steam pressure in chamber 10 tending to push down the spindle q and the force of the spring to together with the steam pressure in the throat of the choke tube t which tend to push up the spindle q. The pressure in the throat of the choke tube t is always proportionately less than the steam pressure in chamber p due to the Venturi action at the throat of the tube. It will be seen therefore that there is always a balancing action between the live steam pressure acting to push down the spindle q and the reduced pressure at the throat of the tube t applied to the spindle q assisted by the pressure of the spring w. This results in an automatic adjustment movement of the spindle q with every change in live steam pressure and gives a reduction in flow area past the spindle through the tube 1? for an increase in live steampressure and vice versa.

What we claim is:

1. In an exhaust steam injector, an automatic auxiliary choke which regulates the area for the flow of live steam to take the place of exhaust steam for working the injector when exhaust steam is not available, in accordance with the pressure of the live steam, said automatic auxiliary choke including a steam inlet tube and a spring controlled movable spindle fitted concentrically therein, said spindle having a diverging conical-like end at the inlet end of the choke tube, the larger end of said movable spindle projecting into a chamber open t the boiler pressure, said pressure tending to push down the conical or stepped end into the choke tube thereby reducing the steam inlet area, this movement being resisted by the proportionate balancing action of the spring and. of the reduced pressure of the steam in the throat of the choke tube.

2. In an exhaust steam injector, an automatic auxiliary choke which regulates the area for the flow of live steam to take the place of exhaust steam for working the injector when exhaust steam is not available, in accordance with the pressure of the live steam, said automaticauxilchoke tube thereby reducing the steam inlet area, this movement being resisted by the proportionate balancing action of the reduced pressure of the steam in the throat of the choke tube.

RICHARD DAVID NIETCALFE. JAMES CROXON METCALFE. 

